Method and apparatus for resecting a greater tubercle from a humerus of a patient during performance of a shoulder replacement procedure

ABSTRACT

A surgical assembly for resecting a greater tubercle from a humerus of a patient during performance of a shoulder replacement procedure. The surgical assembly includes a cutting tool for resecting the greater tubercle from the humerus. The surgical assembly also includes a tool guide member having a tool guide surface defined therein. The tool guide surface is configured to position the cutting tool in a predetermined position relative to the greater tubercle of the humerus. A method of resecting a greater tubercle from a humerus of a patient during performance of a shoulder replacement procedure is also disclosed.

[0001] Cross reference is made to copending U.S. patent application Ser.No. ______ (Attorney Docket No. 1671-0115), entitled “Method andApparatus for Performing a Shoulder Replacement Procedure in theTreatment of Cuff Tear Arthropathy” by Brian Maroney and Ian Trail whichis assigned to the same assignee as the present invention and which isfiled concurrently herewith.

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates generally to a shoulder replacementprocedure, and more particularly to a method and apparatus for resectinga greater tubercle from a humerus of a patient during performance of ashoulder replacement procedure.

BACKGROUND OF THE INVENTION

[0003] During the lifetime of a patient, it may be necessary to performa joint replacement procedure on the patient as a result of, forexample, disease or trauma. One such type of joint replacement procedureis a shoulder replacement procedure in which a diseased and/or damagedshoulder joint is replaced with a prosthetic shoulder joint.

[0004] The need for a shoulder replacement procedure may be created bythe presence of any one of a number of conditions. One such condition isthe deterioration of the patient's rotator cuff. Specifically, an intactrotator cuff stabilizes the humeral head in the glenoid fossa of thescapula during abduction of the arm. While it is stabilized in such amanner, abduction of the arm causes the humeral head to translate only ashort distance in the superior direction (e.g. a few millimeters)whereby a space is maintained between the humeral head and the acromion.However, for patients with rotator cuff arthropathy, significantlygreater humeral excursion is observed. In particular, hyper-translationof the humeral head in the superior direction is observed in patientswith massive rotator cuff deficiency thereby resulting in articulationbetween the superior surface of the humeral head and both the inferiorsurface of the acromion and the acromioclavicular joint during abductionof the patient's arm. Such articulation between these componentsaccelerates humeral articular destruction and erosion of the acromionand acromioclavicular joint. Moreover, such bone-to-bone contact isextremely painful for the patient thereby significantly limiting thepatient's range of motion. In short, patients with massive rotator cufftear and associated glenohumeral arthritis, as is seen in cuff teararthropathy, may experience severe shoulder pain, as well as, reducedfunction of the shoulder.

[0005] In order to treat patients suffering from cuff tear arthropathy,a number of prosthesis and techniques utilizing existing prosthesis haveheretofore been designed. For example, surgeons have heretofore utilizeda relatively large humeral head prosthesis in an attempt to completely“fill” the shoulder joint space. It was believed that such use of alarge prosthesis would increase the efficiency of the deltoid musclethereby improving motion of the shoulder. However, clinical experiencehas shown that such use of a large humeral head prosthesis “overstuffs”the shoulder joint thereby increasing soft tissue tension, reducingjoint range of motion, and increasing shoulder pain. Moreover, such useof an oversized prosthetic head fails to resurface the area of thegreater tubercle of the humerus thereby allowing for bone-to-bonecontact between the greater tubercle and the acromion during abductionof the patient's arm.

[0006] A number of humeral head bipolar prostheses have also beenutilized in an attempt to address the problems associated with cuff teararthropathy. It was believed that the relatively unconstrained motion ofthe bipolar head would improve shoulder motion. However, heretoforedesigned bipolar prosthetic heads include relatively large offsetsthereby overstuffing the shoulder joint in a similar manner to asdescribed above. Moreover, scar tissue may form around the bipolar headthereby “freezing” the dual articulating motion of the prosthesis whichhas been known to create a large hemiarthroplasty that likewiseoverstuffs the shoulder joint. In addition, such bipolar prostheticheads do not cover the articulating surface between the greater tubercleand the acromion thereby creating painful bone-to-bone contacttherebetween.

[0007] Yet further, a number of techniques have heretofore been designedin which the relatively rough surface of the greater tubercle issmoothened with an osteotome or high-speed burr. Although this approachresults in a smoother tubercle contact surface, relatively painfulbone-to-bone articulating contact still occurs thereby reducing thepatient's range of motion.

[0008] What is needed therefore is a method and apparatus for performinga shoulder replacement procedure for use in the treatment of cuff teararthropathy which overcomes one or more of the abovementioned drawbacks.What is particularly needed is a method and apparatus for performing ashoulder replacement procedure which eliminates painful articulationbetween the greater tubercle of the humerus and the acromion.

SUMMARY OF THE INVENTION

[0009] In accordance with one embodiment of the present invention, thereis provided a method of resecting a greater tubercle from a humerus of apatient during performance of a shoulder replacement procedure. Themethod includes the step of securing a tool guide member in apredetermined position relative to the humerus. The method also includesthe step of cutting the greater tubercle with a cutting tool while thetool guide member is secured to the humerus.

[0010] In accordance with another embodiment of the present invention,there is provided an apparatus for guiding a cutting tool duringresection of a greater tubercle from a humerus of a patient duringperformance of a shoulder replacement procedure. The apparatus includesa tool guide member having a tool guide surface defined therein. Theapparatus also includes a positioning member for positioning the toolguide member in a predetermined position relative to the greatertubercle of the humerus.

[0011] In accordance with yet another embodiment of the presentinvention, there is provided a surgical assembly for resecting a greatertubercle from a humerus of a patient during performance of a shoulderreplacement procedure. The surgical assembly includes a cutting tool forresecting the greater tubercle from the humerus. The surgical assemblyalso includes a tool guide member having a tool guide surface definedtherein. The tool guide surface is configured to position the cuttingtool in a predetermined position relative to the greater tubercle of thehumerus.

[0012] It is therefore an object of the present invention to provide anew and useful apparatus for guiding a cutting tool during resection ofa greater tubercle from a humerus of a patient during performance of ashoulder replacement procedure.

[0013] It is moreover an object of the present invention to provide animproved apparatus for guiding a cutting tool during resection of agreater tubercle from a humerus of a patient during performance of ashoulder replacement procedure.

[0014] It is a further object of the present invention to provide a newand useful method of resecting a greater tubercle from a humerus of apatient during performance of a shoulder replacement procedure.

[0015] It is also an object of the present invention to provide animproved method of resecting a greater tubercle from a humerus of apatient during performance of a shoulder replacement procedure.

[0016] It is yet another object of the present invention to provide amethod and apparatus for performing a shoulder replacement procedurewhich eliminates painful articulation between the greater tubercle ofthe humerus and the acromion.

[0017] The above and other objects, features, and advantages of thepresent invention will become apparent from the following descriptionand the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a perspective view of a humeral prosthesis whichincorporates the features of the present invention therein;

[0019]FIGS. 2 and 3 are diagrammatic views which show the humeralprosthesis of FIG. 1 implanted in the body of a patient;

[0020]FIGS. 4 and 5 are views similar to FIGS. 2 and 3, but showing ahumeral prosthesis having a standard, subhemispherically-shaped headcomponent implanted in the body of the patient;

[0021]FIG. 6 is a perspective view of a surgical instrument assemblywhich incorporates the features of the present invention therein; and

[0022] FIGS. 7-15 show a patient's shoulder during the various steps ofa shoulder replacement procedure for the treatment of cuff teararthroplasty according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] While the invention is susceptible to various modifications andalternative forms, a specific embodiment thereof has been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular form disclosed, but on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

[0024] Referring now to FIGS. 1-3, there is shown a modular humeralprosthesis 10 which includes a stem component 12 and a head component14. The stem component 12 includes an elongated stem portion 16 and aproximal body portion 18. It should be appreciated that, as used herein,the words proximal and distal are terms of reference that indicate aparticular portion of a bone or prosthesis component according to therelative disposition of the natural bone or implanted prosthesis.Specifically, the term “proximal” indicates the portion of a componentnearest the torso, whereas distal indicates the portion of a componentfarthest from the torso. Directional terms of reference which are usedherein include superior, inferior, anterior, posterior, medial, andlateral. Such directional terms are used herein according to theircommonly understood anatomical meanings. More specifically, with regardto a person positioned in a standing position, the term “superior” isutilized to mean upward, the term “inferior” means downward, the term“anterior” means forward, the term “posterior” means rearward, the term“medial” means inwardly from the side toward the center of the body, andthe term “lateral” means outwardly from the center of the body towardthe side.

[0025] As shown in FIG. 14, the distal stem portion 16 of the stemcomponent 12 is configured to be implanted into the medullary canal 20of the patient's humerus 22 thereby securing the prosthesis 10 to thehumerus 22. The proximal body portion 18 of the stem component 12extends out of the proximal end of the humerus 22 in order for the headcomponent 14 to be secured thereto. In particular, the head component 14includes a tapered post 24 which is press fit or otherwise received intoa corresponding tapered bore 26 defined in the proximal body portion 18in order to secure the head component 14 to the stem component 12.Preferably, the head component 14 is secured to the stem component 12prior to implantation of the stem component into the medullary canal 20of the patient's humerus, although in situ securement of the headcomponent 14 to the stem component 12 is also contemplated.

[0026] The head component 14 includes an outer bearing surface 28. Theouter bearing surface 28 includes a glenoid-bearing portion 30 and anacromion-bearing portion 32. In particular, as shown in FIGS. 2 and 3,an imaginary line 34 divides the outer bearing surface 28 into (1) afirst portion (i.e. the glenoid-bearing portion 30) which is essentiallythe same configuration as a standard, subhemispherically-shaped headcomponent, and (2) a second portion (i.e. the acromion-bearing portion32) which, in effect, extends the radial distance of the glenoid-bearingportion 30. Specifically, the outer bearing surface 28 extends a radialdistance D in the medial/lateral direction (as viewed in FIGS. 2 and 3).The radial distance D across which the outer bearing surface 28 extendsin the medial/lateral direction is greater than, or equal to, 190degrees (i.e. D≧190°). In a more specific exemplary embodiment, theradial distance D across which the outer bearing surface 28 extends inthe medial/lateral direction is approximately 220 degrees (i.e. D≈220°).However, it should be appreciated that the head component 14 may beconfigured to include an outer bearing surface 28 which extends acrossany desired radial distance between the range of, for example, 190degrees and 270 degrees (i.e. 190°≦D≦270°).

[0027] Use of a prosthetic head component 14 having such a configuration(i.e. an outer bearing surface 28 possessing such an extended radialdistance) is particularly advantageous during performance of a shoulderreplacement procedure in the treatment of cuff tear arthropathy or anyother ailment in which the patient's rotator cuff has been torn orotherwise separated from the humerus 22. In particular, as describedabove, in the absence of the rotator cuff, hyper-translation of thehumeral head (or prosthetic head component) in the superior direction isobserved. During abduction of the arm, such hyper-translation results inarticulation between the humeral head (or prosthetic head component) andthe patient's acromion 36 (along with the acromioclavicular joint).However, in the case of the prosthetic head component 14 of the presentinvention, the additional bearing surface area provided by theacromion-bearing portion 32 provides a low friction surface forarticulating with an inferior surface 38 of the patient's acromion 36thereby reducing, if not eliminating, pain associated with abduction ofthe patient's arm.

[0028] This is a significant improvement over heretofore designedprosthesis. For example, use of a standard, subhemispherically-shapedhead component in regard to the treatment of cuff tear arthropathy isshown in FIGS. 4 and 5. As can been seen, the patient's acromion 36articulates with the low friction outer surface of thesubhemispherically-shaped head component through only approximately 15°of abduction of the patient's arm. Continued abduction of the patient'sarm beyond such a range (i.e. 15°) results in painful bone-to-bonecontact between the patient's acromion 36 and the patient's greatertubercle 40.

[0029] However, as can be seen in FIGS. 2 and 3, a significantly greaterrange of motion may be achieved by use of the prosthetic head component14 of the present invention. In particular regard to the exemplaryembodiment of the head component 14 described herein, the patient'sacromion 36 articulates with the low friction outer surface bearingsurface 28 of the head component 14 through over 60° of abduction of thepatient's arm. This is due, in part, to the replacement of the patient'sgreater tubercle 40 with the acromion-bearing portion 32 of theprosthetic head 14. In particular, as will be discussed below in greaterdetail, during a surgical procedure according to the present invention,the natural head 98 of the patient's humerus 22 is first resected (seeFIG. 7). Thereafter, the patient's greater tubercle 40 is then likewiseresected (see FIG. 14). As a result, when the prosthesis 10 is implantedinto the medullary canal 20 of the patient's humerus 22, theglenoid-bearing portion 30 of the head component 14 corresponds to thenatural head 98 of the patient's humerus 22, whereas theacromion-bearing portion 32 corresponds to the greater tubercle 40 ofthe patient's humerus 22. What is meant herein by the term “correspond”when used in conjunction with a feature of the prosthesis 10 is thatsuch a feature is located in approximately the same anatomic position asthe natural anatomic feature that it replaced. Hence, theglenoid-bearing portion 30 of the head component 14 “corresponds” to thepatient's natural humeral head 98 since it is located in approximatelythe same anatomical position as the natural head 98 subsequent toreplacement thereof, whereas the acromion-bearing portion 32 of the headcomponent 14 “corresponds” to the patient's greater tubercle 40 since itis located in approximately the same location as the greater tubercle 40subsequent to replacement thereof.

[0030] It should be appreciated that resection of the greater tubercle40 is preferably only performed when the patient is suffering from amassive rotator cuff tear. In particular, since the insertion points forcertain of the muscles which form the rotator cuff are located on thegreater tubercle 40, a surgeon would not typically resect the greatertubercle 40 unless the rotator cuff was already torn or otherwiserendered inoperative. This is true since, as described above, therotator cuff, when functionally intact, stabilizes the humeral head inthe glenoid fossa of the scapula during abduction of the arm therebyallowing the humeral head (or implanted prosthetic head component) totranslate only a short distance in the superior direction (e.g. a fewmillimeters) during abduction of the patient's arm. Hence, whenfunctionally intact, the rotator cuff prevents articulation (e.g.bearing contact) between the humeral head (or implanted prosthetic headcomponent) and the patient's acromion 40. As a result, a surgeon wouldbe clinically motivated to leave the greater tubercle 40 intact(including all muscle insertions associated therewith) in most, if notall, cases in which the rotator cuff is functionally intact.

[0031] As can therefore be appreciated from the above description, asused herein in regard to the greater tubercle 40, the terms “resect”,“resecting”, “resection”, and “resected”, when utilized to refer to theconcepts of the present invention, are intended to mean any cutting orremoval of a significant portion of the greater tubercle 40 includingcertain l10 portions of the tubercle 40 utilized for muscle insertion.Hence, “resection” of the greater tubercle 40, as utilized herein, isintended to refer to the removal of greater portions of the greatertubercle 40 than would be removed in the case in which the surgeondesires to substantially retain the greater tubercle 40 in itspreoperative condition and/or function such as in the case of when thesurgeon desires to retain the functionality of the rotator cuff. Forexample, “resection” of the greater tubercle 40 may include the removalof bone associated with the greater tubercle to a point beyond theinsertion point of the supraspinatus muscle. In any case, the term“resection” of the greater tubercle 40, as utilized herein, is intendedto mean bone material removal to a degree beyond any slight shaving,smoothening, or “deburring” of the greater tubercle.

[0032] Referring now to FIG. 6, there is shown a surgical instrumentassembly such as a cutting tool guide assembly 50 which is utilizedduring performance of a shoulder replacement procedure according to thepresent invention. The tool guide assembly 50 is particularly useful forguiding a cutting tool such as an oscillating bone saw or osteotomeduring cutting of the greater tubercle 40. For example, if duringperformance of a shoulder replacement procedure, a surgeon discoversthat the patient's rotator cuff is torn or otherwise renderedinoperative due to, for instance, cuff tear arthropathy, the surgeon mayutilize the tool guide assembly 50 during resection of the patient'sgreater tubercle 40 in order to allow for the use of the prosthetic headcomponent 14.

[0033] The tool guide assembly 50 includes support block 52, a rightguide member or block 54, a left guide member or block 56, and afastener 58. The support block 52 includes a channel 60 which defines amortise 62 for slidably receiving a projection or tenon 64 associatedwith the guide blocks 54, 56. In such a manner, the mortise 62 and thetenon 64 define a dovetail joint 66 which is utilized to selectivelysecure one of the guide blocks 54, 56 to the support block 52.

[0034] The guide blocks 54, 56 are securable to the humerus 22 of thepatient in order to guide the surgeon during cutting of the greatertubercle 40. In particular, the support block 52 may first be secured tothe humerus 22 by use of a positioning member. The positioning membermay take any one of a number of different forms. For instance, in oneexemplary embodiment, the positioning member may take the form of asurgical instrument such as an intramedullary broach 68 (see FIG. 9) oran intramedullary reamer 70 (see FIG. 8). In the case of the broach 68,as shown in FIGS. 9 and 10, the support block 52 is secured to aproximal end portion of the broach 68. Specifically, the broach 68includes a distal end portion 72 which is advanced into the medullarycanal 20 of the humerus 22 during a broaching operation. A proximal endportion 74 of the broach 68, on the other hand, extends out of themedullary canal 20, as shown in FIG. 9. The proximal end portion 74 ofthe broach 68 has a collar 76 having a face 78 and a slot 80 definedtherein. A positioning tab 82 associated with the support block 52 isreceived into the slot 80 of the broach collar 76. Thereafter, thefastener 58 is utilized to secure the support block 52 to the broach 68.Specifically, a threaded end portion 84 of the fastener is advancedthrough a countersunk hole 86 defined in the base 88 of the supportblock 52 and into a counterbored hole 90 defined in the proximal endportion 74 of the broach 68. The threaded end portion 84 thenthreadingly engages a corresponding threaded portion of the counterboredhole 90 so as to advance and retain a bottom surface 92 of the base 88of the support block 52 into firm contact with the face 78 of the collar76 thereby securing the support block 52 to the broach 68 (see FIGS. 10and 11).

[0035] It should be appreciated that, in lieu of the fastener 58, otherconfigurations for securing the support block 52 to the broach 68 mayalso be utilized in accordance with the principles of the presentinvention. For example, in lieu of the fastener 58, a taper assemblysuch as a Morse taper assembly, a multi-sided post such as ahexagon-shaped post, or a clamping mechanism for clamping to the collar76 may be utilized to secure the support block 52 to the broach 68.

[0036] In any event, once the support block 52 is secured to the broach68, the tenon 64 of either the right guide block 54 or the left guideblock 56 (depending on whether the surgeon is operating on the patient'sright or left humerus) is then slid into the mortise 62 of the supportblock 52. A pair of spring plungers (not shown) are utilized to retainthe guide blocks 54, 56 in a desired location relative to the supportblock 52. As shown in FIG. 13, the configuration of the guide blocks 54,56 and the support block 52 positions a tool guide surface 94 defined inthe guide blocks 54, 56 in a predetermined location relative to thepatient's humerus 22. In particular, the dimensions of the support block52 and the guide blocks 54, 56 are predetermined so as to position thetool guide surface 94 in a location in which a surgeon may utilize theguide surface 94 to remove a predetermined portion of the patient'sgreater tubercle 40. For example, if a surgeon utilizes the guidesurface 94 to guide a reciprocating bone saw 96 (see FIG. 14) orosteotome (not shown), a predetermined portion of the patient's greatertubercle 40 may be resected so as to allow for subsequent implantationof the prosthetic head component 14.

[0037] As shall be described below in regard to a shoulder replacementprocedure according to the present invention, significant advantages areachieved by utilizing the implanted broach 68 as a positioning memberfor positioning the support block 52 (and hence the guide blocks 54, 56)in a desired position relative to the patient's humerus 22. However,certain of such advantages may be achieved by utilizing other types ofpositioning members for positioning the support block 52 (and hence theguide blocks 54, 56) in a desired position relative to the patient'shumerus 22. For example, different types of surgical instruments may beutilized as positioning members for positioning the support block 52(and hence the guide blocks 54, 56) in a desired position relative tothe patient's humerus 22. For instance, as alluded to above, the supportblock 52 may be secured to a portion of the elongated shaft of anintramedullary reamer 70. Alternatively, the support block 52 may besecured to a trial implant stem (not shown) or to the implant stem (notshown) itself.

[0038] Moreover, either the support block 52, or the guide blocks 54, 56themselves, may utilize a positioning member which allows the blocks 52,54, 56 to be secured directly to the humerus 22 thereby eliminating theneed to utilize a surgical instrument (e.g. the broach 68, reamer 70,trial implant stem, or implant stem) as a positioning member. In such aconfiguration, the support block 52 or the guide blocks 54, 56 may beconfigured to be utilized in conjunction with an attachment mechanismsuch as a pin assembly, clamping mechanism, or the like (not shown) forsecuring the same to the humerus 22 in a predetermined position relativeto the humerus 22.

[0039] Yet, further, the positioning member may also take the form of afixture assembly or the like (not shown) which positions the supportblock 52 and/or the guide blocks 54, 56 in a predetermined positionrelative to the humerus 22 without actually being secured to the humerus22. Specifically, such a fixture assembly may be secured to any one ofthe number of surgical components which are utilized during performanceof a shoulder replacement procedure thereby eliminating the need tosecure the support block 52 and/or the guide blocks 54, 56 to thehumerus 22.

Operation of the Present Invention

[0040] In operation, the concepts of the present invention may beutilized to surgically treat a patient suffering from cuff teararthropathy during performance of a shoulder replacement procedure. Inorder to do so, as shown in FIG. 7, the head 98 of the patient's humerus20 is first resected by use of, for example, a bone saw 100. Inparticular, a head resection guide assembly 102 is first secured to theproximal end portion of the patient's humerus 22 in a conventionalmanner. A cutting guide 104 associated with the assembly 102 is thenutilized to guide the blade of the bone saw 100 along a desired cuttingpath (shown as the dashed line 106) in order to resect a desired portionof the patient's natural head 98. It should be appreciated that the headresection procedure shown in FIG. 7 and described herein is quitesimilar to heretofore utilized head resection procedures which have beenused during performance of shoulder replacement procedures in which thepatient's rotator cuff is functionally intact (or believed to befunctionally intact).

[0041] Once the natural head 98 of the patient's humerus 22 has beenresected, the medullary canal 20 of the patient's humerus 22 is thensurgically prepared. Specifically, as shown in FIG. 8, the reamer 70 isadvanced into the medullary canal 20 of the patient's humerus 22 inorder to ream the same. As with the head resection process describedabove in regard to FIG. 7, the reaming procedure shown in FIG. 8 anddescribed herein is quite similar to heretofore utilized reamingprocedures which have been used during performance of shoulderreplacement procedures in which the patient's rotator cuff isfunctionally intact (or believed to be functionally intact).

[0042] Subsequent to reaming the medullary canal 20 of the humerus 22, abroaching procedure is performed in order to further prepare themedullary canal 20 for implantation of the stem component 12 of theprosthesis 10. Specifically, the distal end portion 72 of the broach 68is advanced into the medullary canal 20 of the humerus 22 to a positionin which the proximal end portion 74 of the broach 68 extends out of themedullary canal 20. As shown in FIG. 9, the broach 68 is advanced intothe medullary canal 20 until fully seated in a position in which thecollar 76 of the broach sits substantially flush with the resectedsurface of the humerus 22. Such broaching of the humerus 22, amongstother things, forms a cavity which is substantially equivalent in shapeto the proximal body portion 74 of the stem component 68 (albeitslightly smaller to allow for press fitting of the stem component 68).Again, as with the head resection and reaming processes described above,the broaching procedure shown in FIG. 9 and described herein is quitesimilar to heretofore utilized broaching procedures which have been usedduring performance of shoulder replacement procedures in which thepatient's rotator cuff is functionally intact (or believed to befunctionally intact).

[0043] At this point, if the surgeon determines (or had previouslydetermined) that the patient's rotator cuff is torn or otherwise nolonger functionally intact, the surgeon may opt to prepare the patient'shumerus 22 for implantation of a prosthesis that includes the prosthetichead component 14. In order to do so, the patient's greater tubercle 40must first be resected. The steps associated with such resection of thepatient's greater tubercle 40 are depicted in FIGS. 10-14. The first ofsuch steps, as shown in FIG. 10, is the securement of the support block52 to the broach 68. In particular, the positioning tab 82 associatedwith the support block 52 is first advanced into the slot 80 of thebroach collar 76. Thereafter, the fastener 58 is utilized to secure thesupport block 52 to the broach 68. Specifically, the threaded endportion 84 of the fastener 58 is advanced through the countersunk hole86 defined in the base 88 of the support block 52 and into threadingengagement with the threaded portion of the counterbored hole 90.Rotation (i.e. tightening) of the fastener 58 causes the bottom surface92 of the base 88 of the support block 52 to be advanced into firmcontact with the face 78 of the collar 76 thereby securing the supportblock 52 to the broach 68 (see FIG. 10).

[0044] Once the support block 52 has been secured to the broach 68 insuch a manner, the surgeon secures either the right guide block 54 orthe left guide block 56 to the support block 52. Specifically, if thesurgeon is performing the procedure on the patient's right shoulder, thesurgeon selects the right guide block 54. Conversely, if the surgeon isperforming the procedure on the patient's left shoulder, the surgeonselects the left guide block 56. In either case, as shown in FIG. 12,the tenon 64 of either the right guide block 54 or the left guide block56 (again, depending on whether the surgeon is operating on thepatient's right or left humerus) is slid into the mortise 62 of thesupport block 52. The block 54, 56 is advanced to a desired lateralposition relative to the humerus 22 at which time a pair of springplungers (not shown) are utilized to retain the guide blocks 54, 56 in adesired location relative to the support block 52.

[0045] As shown in FIG. 13, the configuration of the guide blocks 54, 56and the support block 52 positions the tool guide surface 94 defined inthe guide blocks 54, 56 in a predetermined location relative to thepatient's humerus 22. In particular, the configuration of the supportblock 52 and the guide blocks 54, 56, when secured to the humerus 22 byuse of the implanted broach 68, position the tool guide surface 94 in alocation in which a surgeon may utilize the guide surface 94 to remove apredetermined portion of the patient's greater tubercle 40.

[0046] Indeed, once the required guide block 54, 56 has been secured tothe support block 52 in the manner described above, a surgeon mayutilize the guide surface 94 to guide a reciprocating bone saw 96 (seeFIG. 14) or osteotome (not shown) in order to resect a predeterminedportion of the patient's greater tubercle 40. Such resection isperformed to provide for subsequent implantation of the prosthetic headcomponent 14 during treatment of a patient suffering from cuff teararthropathy.

[0047] Once the surgeon has completed the resection of the greatertubercle 40 by use of the bone saw 96, the surgeon disassembles the toolguide assembly 50 from broach 68. Specifically, the right guide block 54or the left guide block 56 (depending on which one was utilized) isdetached from the support block 52. Thereafter, the fastener 58 isunscrewed or otherwise removed from the broach 68 thereby allowing thesupport block 52 to be lifted away from the face 78 of the collar 76.

[0048] It should be appreciated that subsequent to removal of the toolguide assembly 50, a rasp or rongeur (not shown) may be utilized toextend the length of the cut created by the saw blade of the bone saw 96in a medial direction to the point in which it intersects with theoblique cut created by the bone saw 100 during resection of the naturalhead 98 of the patient's humerus 22 (see FIG. 7). Moreover, the rasp orrongeur may also be utilized to remove any protruding bone sectionswhich may subsequently interfere with proper seating of the prosthesis10.

[0049] Once the surgeon has completed his or her use of the rasp orrongeur, the broach 68 is extracted from the medullary canal 22.Thereafter, the surgeon prepares the prosthesis 10 for implantation intothe patient's humerus 22. Specifically, the surgeon selects both a stemcomponent 12 and a head component 14 from a number of available sizes inorder to select components which are properly sized for the patient'sanatomy. It should be appreciated that the surgeon may employ any one ofnumerous techniques to determine the proper size of the stem component12 and the head component 14 including the use of trial components whichmay be temporarily implanted into the humerus 22. For example, thesurgeon may secure a trial head component to the broach 68 prior toextraction of the broach 68 in order to determine the proper size of thehead component. It should also be appreciated that the surgeon generallyselects a head component 14 which is sized quite similarly to the sizeof the patient's natural anatomy. This is a significant distinction fromheretofore utilized methods in which the surgeon would generally selecta head component which is larger in size than the natural head thereby“overstuffing” the shoulder joint as described above.

[0050] In any event, once the final combination of a properly sized stemcomponent 12 and head component 14 has been selected, the two componentsare secured to one another. An impaction stand and associated impactor(not shown) may be utilized to engage the Morse taper associated withthe two components. Specifically, the impaction stand and the impactorare utilized to advance and lock the tapered post 24 of the headcomponent 14 into the corresponding tapered bore 26 defined in theproximal body portion 18 of the stem component 12 in order to secure thehead component 14 to the stem component 12. Thereafter, as shown in FIG.14, the prosthesis 10 is implanted into the medullary canal 20 of thepatient's humerus 22.

[0051] Hence, as described herein, each of the prosthesis 10, thecutting tool guide assembly 50, and the associated surgical method ofthe present invention provides numerous advantages over heretoforedesigned prostheses, instrument assemblies, and surgical methods. Forexample, use of a prosthesis which includes the prosthetic headcomponent 14 is particularly advantageous during performance of ashoulder replacement procedure in the treatment of cuff tear arthropathyor any other ailment in which the rotator cuff has been torn orotherwise irreparably separated from the humerus 22. In particular, asdescribed above, in the absence of the rotator cuff, hyper-translationof the humeral head (or prosthetic head component) in the superiordirection is observed. During abduction of the patient's arm, suchhyper-translation results in articulation between the humeral head (orprosthetic head component) and the patient's acromion 36 (see FIGS. 2and 3). However, in the case of the prosthetic head component 14 of thepresent invention, the additional bearing surface area provided by theacromion-bearing portion 32 provides a low friction surface forarticulating with an inferior surface 38 of the patient's acromion 36thereby reducing, if not eliminating, pain associated with abduction ofthe patient's arm.

[0052] Moreover, the prosthetic head component 14 may be utilized withexisting stem component designs. This is particularly useful since iteliminates the need to design a dedicated stem component for use onlywith the head component 14. As a result, a hospital or medical facilitymay reduce the number of different types of stem components which mustbe maintained in its inventory since the same stem component may beutilized for either a standard, subhemispherically-shaped prosthetichead component or the head component 14 of the present invention.

[0053] Yet further, the cutting tool guide assembly 50 of the presentinvention provides for relative ease in the resection of the greatertubercle 40. Specifically, the tool guide assembly 50 provides asurgical instrument assembly which may be utilized by the surgeon toeasily and accurately determine the proper cutting plane for resectingthe greater tubercle 40. Such an assembly does not exist in heretoforedesigned surgical instrument assemblies.

[0054] Moreover, the cutting tool guide assembly 50 of the presentinvention provides for relatively efficient resection of the greatertubercle 40 since, in certain exemplary embodiments, it is designed tobe secured to the broach 68. Indeed, by configuring the cutting toolguide assembly 50 to be secured to the broach 68, additional timeconsuming surgical steps are avoided. Specifically, by securing thecutting tool guide assembly 50 to the broach 68, use of additionalsupport members such as additional surgical instruments is avoided.

[0055] Yet further, the surgical method of the present inventionprovides flexibility in regard to the type of procedure which may beperformed by the surgeon. In particular, since the initial steps of thesurgical procedure of the present invention (e.g. the steps up to andincluding broaching of the medullary canal 20 of the humerus 22) aresubstantially the same as those steps which would be performed in thecase of when the rotator cuff is intact, the surgeon may make thedecision to resect the greater tubercle 40 (and thereafter utilize theprosthetic head component 14) in situ. For example, if the surgeonbegins a shoulder replacement procedure under the belief that therotator cuff is somewhat intact only to find out during the procedurethat the rotator cuff is, in fact, functionally inoperative, the surgeonmay “convert” the procedure into a procedure which also “replaces” thegreater tubercle 40 by simply attaching the cutting guide assembly 50 tothe broach 68 (which would be present anyway) and thereafter completingthe procedure (including the use of the prosthetic head 14 as opposed toa standard, subhemispherically-shaped head) in the manner describedabove. Hence, the surgical procedure of the present invention isparticularly useful in clinical situations in which the surgeon cannotaccurately determine preoperatively the condition of the patient'srotator cuff.

[0056] While the invention has been illustrated and described in detailin the drawings and foregoing description, such an illustration anddescription is to be considered as exemplary and not restrictive incharacter, it being understood that only the preferred embodiment hasbeen shown and described and that all changes and modifications thatcome within the spirit of the invention are desired to be protected.

[0057] There are a plurality of advantages of the present inventionarising from the various features of the prosthesis, surgical instrumentassembly, and associated methods described herein. It will be noted thatalternative embodiments of each of the prosthesis, surgical instrumentassembly, and associated methods of the present invention may notinclude all of the features described yet still benefit from at leastsome of the advantages of such features. Those of ordinary skill in theart may readily devise their own implementations of a prosthesis,surgical instrument assembly, and/or associated methods that incorporateone or more of the features of the present invention and fall within thespirit and scope of the present invention as defined by the appendedclaims.

What is claimed is:
 1. A method of resecting a greater tubercle from ahumerus of a patient during performance of a shoulder replacementprocedure, said method comprising the steps of: securing a tool guidemember in a predetermined position relative to said humerus; and cuttingsaid greater tubercle with a cutting tool while said tool guide memberis positioned in said predetermined position relative to said humerus.2. The method of claim 1, wherein said step of securing said tool guidemember in said predetermined position relative to said humerus includesthe steps of: advancing a surgical instrument into a medullary canal ofsaid humerus such that (i) a distal end portion of said surgicalinstrument is positioned in said medullary canal, and (ii) a proximalend portion of said surgical instrument extends out of said medullarycanal, and securing said tool guide member to said proximal end portionof said surgical instrument subsequent to said advancing step.
 3. Themethod of claim 2, wherein: said surgical instrument includes anintramedullary broach having a superior face, and said step of securingsaid tool guide member to said proximal end portion of said surgicalinstrument includes the step of securing said tool guide member to saidsuperior face of said intramedullary broach.
 4. The method of claim 2,wherein: said surgical instrument includes an intramedullary reamerhaving an elongated shaft, and said step of securing said tool guidemember to said proximal end portion of said surgical instrument includesthe step of securing said tool guide member to said elongated shaft ofsaid intramedullary reamer.
 5. The method of claim 2, wherein said stepof securing said tool guide member to said proximal end portion of saidsurgical instrument includes the steps of: securing a support block tosaid proximal end portion of said surgical instrument, and securing saidtool guide member to said support block.
 6. The method of claim 5,wherein said step of securing said support block to said proximal endportion of said surgical instrument includes the step of securing saidsupport block to said proximal end portion of said surgical instrumentwith a threaded fastener.
 7. The method of claim 5, wherein: saidsurgical instrument includes an intramedullary broach having a superiorface, and said step of securing said support block to said proximal endportion of said surgical instrument includes the step of securing saidsupport block to said superior face of said intramedullary broach.
 8. Anapparatus for guiding a cutting tool during resection of a greatertubercle from a humerus of a patient during performance of a shoulderreplacement procedure, said apparatus comprising: a tool guide memberhaving a tool guide surface defined therein; and a positioning memberfor positioning said tool guide member in a predetermined positionrelative to said greater tubercle of said humerus.
 9. The apparatus ofclaim 8, wherein said positioning member is configured to secure saidtool guide member to said humerus.
 10. The apparatus of claim 8,wherein: said positioning member includes a surgical instrument which isconfigured to be positioned in a medullary canal of said humerus, whensaid surgical instrument is positioned into said medullary canal of saidhumerus (i) a distal end portion of said surgical instrument ispositioned in said medullary canal, and (ii) a proximal end portion ofsaid surgical instrument extends out of said medullary canal, and saidtool guide member is configured to be secured to said proximal endportion of said surgical instrument.
 11. The apparatus of claim 10,wherein: said surgical instrument includes an intramedullary broachhaving a superior face, and said tool guide member is configured to besecured to said superior face of said intramedullary broach.
 12. Theapparatus of claim 10, wherein: said surgical instrument includes anintramedullary reamer having an elongated shaft, and said tool guidemember is configured to be secured to said elongated shaft of saidintramedullary reamer.
 13. The apparatus of claim 10, further comprisinga support block, wherein: said support block is configured to be securedto said proximal end portion of said surgical instrument when saidsurgical instrument is positioned in said medullary canal of saidhumerus, and said tool guide member is configured to be secured to saidsupport block.
 14. The apparatus of claim 13, further comprising athreaded fastener for securing said support block to said proximal endportion of said surgical instrument when said surgical instrument ispositioned in said medullary canal of said humerus.
 15. The apparatus ofclaim 13, wherein: said surgical instrument includes an intramedullarybroach having a superior face, and said support block is configured tobe secured to said superior face of said intramedullary broach when saidintramedullary broach is positioned in said medullary canal of saidhumerus.
 16. A surgical assembly for resecting a greater tubercle from ahumerus of a patient during performance of a shoulder replacementprocedure, said surgical assembly comprising: a cutting tool forresecting said greater tubercle from said humerus; and a tool guidemember having a tool guide surface defined therein, said tool guidesurface being configured to position said cutting tool in apredetermined position relative to said greater tubercle of saidhumerus.
 17. The surgical assembly of claim 16, further comprising asurgical instrument which is configured to be positioned in a medullarycanal of said humerus, wherein: when said surgical instrument ispositioned in said medullary canal of said humerus (i) a distal endportion of said surgical instrument is positioned in said medullarycanal, and (ii) a proximal end portion of said surgical instrumentextends out of said medullary canal, and said tool guide member isconfigured to be secured to said proximal end portion of said surgicalinstrument.
 18. The surgical assembly of claim 17, wherein: saidsurgical instrument includes an intramedullary broach having a superiorface, and said tool guide member is configured to be secured to saidsuperior face of said intramedullary broach.
 19. The surgical assemblyof claim 17, wherein: said surgical instrument includes anintramedullary reamer having an elongated shaft, and said tool guidemember is configured to be secured to said elongated shaft of saidintramedullary reamer.
 20. The surgical assembly of claim 17, furthercomprising a support block, wherein: said support block is configured tobe secured to said proximal end portion of said surgical instrument whensaid surgical instrument is positioned in said medullary canal of saidhumerus, and said tool guide member is configured to be secured to saidsupport block.